Pip Coory has shed more tears than she'd care to admit in the pursuit of vindication.

For more than 3 years, the Springston homeowner has fought to convince the Earthquake Commission (EQC) and insurer State that her house cannot be repaired for less than the commission's $100,000 cap.

EQC first assessed the damage at $30,000. Coory rejected it.

Following a re-assessment, a cash settlement for $80,000 was paid into her bank account after EQC suspected the house could have watertightness issues. Coory sent the money back.

Although the house was clad in a material commonly found in leaky buildings, she said hers was brick underneath.

State's first assessment came back at $120,000 but Coory said she was told the insurer could not intervene while it was under cap.

Last week, after "hundreds of emails, a huge number of reports and lots and lots of tears", the parties agreed the damage was over cap.

Coory declared it "the best day of my life".

"I've got a 20-minute drive into work every day and there's a particular stretch of road [on which] I pretty much cried every day. I've had no happy moments."

She had engaged a lawyer and was preparing for a court battle when a State representative phoned with the news.

In her view, the EQC assessments had been incomplete and inaccurate. Professional reports countering EQC's views were ignored.

Coory's quantity surveyor assessed the repairs at more than $900,000.

"My biggest frustration is that it's taken this long. [EQC] just kept closing the door [and] didn't want to accommodate the fact that they were wrong."

She "hounded" EQC for a joint review with State after highlighting her plight in The Press in December.

Coory also made a case to State's parent company, IAG, in Australia. "I just said, ‘I can't live like this'. I've got a vibrating house and every night I'm woken up by loud banging.

"I've literally screamed at them at times, [saying] ‘You are my insurer, how can you leave me like this?'."

EQC Canterbury home repair programme general manager Reid Stiven said after reviewing the property EQC and State had agreed on a "slightly different repair strategy than was originally decided upon".

"This, in conjunction with allowing for current costs being higher than they were two years ago, has meant that the cost to repair the earthquake damage has gone from just under cap to just over cap," he said.

Homes with pre-existing risk factors were usually cash settled because repair work could be "fraught with legal risk", Stiven said.

"We have explained our position to [Coory] and understand that the conversations that have taken place have been undoubtedly difficult for her."

IAG spokeswoman Renee Walker confirmed State's damage assessment in May last year was about $120,000.

"We communicated this with EQC and requested a joint review, however, given that their assessment was under cap, and ours was close to cap, they declined this request. With the information available at the time, we had no reason to believe that this was not the best outcome for Ms Coory," she said.